I have frequent problems with Spotify not working properly. There are lots of times when it doesn't log in and it can forget all my favourites at any time and then it will sometimes bring them back randomly. It can be playing my favourite songs and yet they don't appear in the favourites list. If I'm lucky, the last song that I added might show up.
Sometimes resetting the system (pressing and holding both scroll wheels on the steering wheel) can bring everything back.

the spotify in my car doesn't store favourites, regardless of whether i use the Tesla default account or my own. i just order songs to play via voice control, works 80% of the time. sometimes it just doesn't connect and i just listen to the local radio instead.